Not since Quake Test have so many played such a small chunk of such an exciting game for so long. The first two Diablo games mixed the compulsive character progression of an RPG with the reactive combat of an action game, and Diablo III refines both. It's going to be the drug of choice for the addiction-prone PC gamer in 2012. And we know this because we're playing the same small chunk of it – a modest beta version – over and over again.
Interestingly, though, it's not quite the same chunk each time we play it. Not just because of some randomised side quests and environments, but because we're getting to see Blizzard revise and overhaul the game as it gets closer to completion. Quite drastically, it turns out.
Until recently, one of the five classes you can choose from was rather underwhelming. The crossbow-based Demon Hunter had a few fun abilities, but she felt much more vulnerable than the other classes, without any extra damage output to make up for it. But as Blizzard shuffle skills around, changing damage percentages and the order in which they unlock, they've given the Demon Hunter some much-needed muscle.
An early Demon Hunter skill called Impale is now powerful enough to give her an edge: it's a fast, high-damage projectile with almost no cooldown. It makes the Demon Hunter an assassin: with a full reserve of her main resource, Hatred, she can fire a flurry of these in rapid succession to cut down a boss monster brutally fast.
Soon after, she unlocks Rapid Fire. It's a torrent of arrows that costs a chunk of Hatred to start, but is relatively cheap to sustain if you keep holding the button down. It gives her a satisfying crowd control ability, and adds an interesting layer of strategy: often it's more costefficient to keep firing between groups of enemies than to stop and restart.
Between them, they define the role of the Demon Hunter better than before: she's the only class for whom it's cheap to take out single bosses, but costly to deal with crowds.
There's also been a universal change in Blizzard's take on how customising your character should work. Previously, you could switch between any and all skills you have access to, at any time. You had limited slots, but there was nothing to stop you putting something else in them midcombat. Now, you can only do that at Altars of Nephalem, stones found in town and at major checkpoints.
The previous system was pretty ridiculous, in terms of the potential exploits, but it also feels needlessly awkward now to trek back to town every time you want to tweak your build – why not just let us change skills any time we're not in combat?
The general combat balance of Diablo III makes it magnificently fun: you butcher and frazzle enemies in seconds, and every skill feels ferociously powerful. But that did make it conspicuously easy. In the new beta, your powers are still devastating, but more of the monsters you encounter are vicious too. The Wizard finally feels vulnerable when mobbed, and death is no longer unheard of.
The best of the difficulty tweaks do more than rebalance the numbers. Some boss monsters now have the ability to spawn floating points of purple light that fire out a beam of death that rotates around them. In frighteningly short order, you can find yourself surrounded by deadly clockfaces, dashing to avoid their swinging hands. They're one of the few things in Diablo that force you to manoeuvre precisely in order to stay alive, and I've died at least once every time the bastard things crop up. They're brilliant.
It's a bit of a pain that you have to connect to Blizzard's servers even to play singleplayer, but if they continue to tweak the algorithms and add new features like this after launch, it may be worth it. Particularly in a randomised game, encountering something you didn't know existed is a great experience.
Replaying it so many times has revealed an interesting difference in the way your character develops compared with the previous games. Almost everything, even the magical spells you cast as a Wizard, depends entirely on the weapon in your hands. When I fire an Arcane Orb, a glowing magical projectile that explodes on impact, the damage it does to the zombies across the room is a function of how sharp the sword in my hands is.
It's a strange idea, but a good game mechanic: it means equipment is equally important to all classes, so Wizards can get as excited about loot as Barbarians do. It also means that if your character is struggling to keep up with the monsters, a trip to the blacksmith will usually fix it.
The formula is still evolving, and it's exciting to see Blizzard work so fast. Diablo III is already slicker and more satisfying than any other action RPG out there; it's almost scary to think how good it's going to be next year.